The telecom industry requires significant numbers of single phase rectifiers. Usually, single phase rectifiers operate from 120 volts, 240 volts, or 208 volts AC input, with 12 volts, 24 volts, or 48 volts DC output. The current output may be as much as 125 or 150 amperes, at any of those DC voltage ratings.
The prior art has generally provided rack mounted cabinets for mounting in 19 inch or 23 inch relay racks. The cabinets have generally been quite large, and the industry has always prepared its cabinets in such a manner that the cabinets are first built and assembled except for their front cover, which is often assembled to the cabinet but hingedly opened; and the components of the single phase rectifier are then assembled into the cabinet. An industry standard for low frequency magnetic regulated single phase rectifiers operating at 48 volts and 100 amperes has been for a 19 inch relay rack cabinet to be 35 to 42 inches high. By the present invention, an equivalent rated single phase rectifier is mounted in a 19 inch relay rack cabinet that is only 17.5 inches high. Moreover, in keeping with the present invention, single phase rectifiers assembled as described hereafter have more efficient cooling, lower temperature rise and lower audible noise than such previous units of equivalent rating.
The present inventor has analyzed the assembly of prior art devices, and has determined that a number of factors can be significantly improved. They include the matter of physical assembly into a cabinet, which requirement has been obviated by the present invention; the matter of wiring to be assembled and put into place as the electrical components are assembled into the cabinet, requiring a significant amount of wire and other material and providing greater chances for error to occur, a matter that once again has been obviated; the use of transformer and saturable reactor designs that are inherently quite noisy, a matter that once again has been obviated by the present invention; and the problems of inadequate cooling air flow through the cabinet, once again being a matter that is obviated by the present invention.
Turning first to the cabinet design itself, it has been determined that if a strong chassis comprising a horizontal base and a vertical rear wall is assembled, where the material of the base and rear wall are strong and heavy enough to carry all of the loads that may be placed upon them by the components mounted to them and by the relay rack mounting of the unit, then it is not necessary for the cabinet structure--at least the side walls and the cabinet top cover--to be other than physical barriers protecting the components mounted within the enclosure. The front door panel may also be of significantly lower weight and thickness construction, because generally only a supervisory control panel is mounted to it.
The use of advanced design of magnetics and their mounting--particularly of the input transformer and the saturable reactor which are physically quite large--reduces the audible noise of the single phase rectifier. In particular, the present invention contemplates that the input transformer has a UI structure rather than the more usual EI structure; whereas the saturable reactor may have an EI core type structure rather than the usual EI shell type structure. In any event, the air spaces are provided around all of the windings mounted on the core legs to allow for adequate flow of cooling air.
In particular, by the provision of an adequate spacing between the windings mounted on the legs of the lower mounted UI input transformer, air flow can be induced upwardly past the transformer to cool the saturable reactor, diode assembly and other components. Indeed, since the flow of air is convection flow, the cooling is adequate and there is no necessity for forced air cooling in enclosures for single phase rectifiers according to the present invention. The cooling air is directed at and through the components to be cooled, so temperature rise within the cabinet enclosure is minimized.
By properly mounting the components of the single phase rectifier, all electrical wiring connections can be brought out to the front of the assembly. The components can, for the most part, be mounted first and thereafter the electrical wiring connections can be made. This reduces the chance for error to occur, and surprisingly also reduces the amount of material being used. The electronic circuitry of the single phase rectifier is not a subject of the present invention. Typical patents for battery chargers in the name of the present inventor are U.S. Pat. Nos. 4,320,333 issued Mar. 16, 1982 and 4,399,396 issued Aug. 16, 1983.